The present disclosure relates to electronic circuits, systems and apparatuses, and in particular, to audio interface circuits and methods.
Recently, the complexity and functionality of handheld electronic devices has accelerated at an ever increasing pace. More and more features and functions are being added to electronic devices such as cellular phones, tablet computers, portable music players, cameras, fitness devices, and even wrist watches. As the functionality of such devices increases, so too does the complexity of the electronic circuits in such devices.
However, these devices often share one common constraint—small size and limited surface area. As the complexity and functionality of the devices increases, it becomes increasingly important to access internal circuits and functionality to both relay information to an end user and determine the operating conditions of various system components during the manufacturing of the device or to evaluate failures of devices in the field.
For example, as illustrated in electronic device 100 of FIG. 1, many contemporary electronic devices are limited to two electrically wired input/output (I/O) ports—i.e., a Universal Serial Bus (USB) port 101 and an audio port 102. USB ports are typically used to communicate data (e.g., D+/D−) between the device electronics 103 and USB circuitry 105 and another external computer system (not shown), for example, and are often used to receive power (e.g., V+ and ground) to power the electronic device and/or charge a battery in the electronic device (not shown). Audio ports typically receive an audio jack which may include a microphone input (Mic) and left and right stereo outputs. Accordingly, an audio signal may be received on the Mic input and coupled to audio circuits 106. The audio circuits may also generate a stereo output, for example.
Therefore, the reduction in size and increase in complexity of modern electronic devices exacerbates the problem faced by system manufacturers and end users to access the growing amount of information inside such devices.